Known ground washers are generally flat or of a square cone design. Under load, flat washer tend to exert a clamp load in a non-specific path. In other words, flat washers may not be centered around a mating bolt, which leads to uneven load on a grounding terminal. As a result, with terminal shift or corrosion, for example, the ground path can be lost. Another problem with flat washers, as with square-cone washers, is that they are not accustomed to prevent loosening of the joint, especially when subjected to vibration. Yet another problem with square-cone washers is that they only provide a minimum amount of contact with the grounding terminal, thereby adversely affecting the overall performance of the assembly. The present invention addresses the foregoing problems and other problems of these and other prior designs. In general, grounding washers according to the principles of the present invention provide a new and innovative method of grounding an electrical circuit to a metal or other conducting surface.
In one embodiment of the present invention, there is provided a washer having a centrally formed column or cylinder that is adapted to take the clamp load of the associated grounding screw as a column load. The washer of the present invention is configured to include a spring portion that is adapted to press on the remainder of the grounding terminal with substantially even force. The washer of the present invention is designed to provide an improved ground path over a greater period of time as compared to known flat washers and other washers. A feature of the compressible portion of the washer is that it creates a spring load to minimize unwanted loosening of the joint.
Preferably, the ground washer and associated screw can be assembled together as a single-unit, known as a “SEMS” design. In one situation, a screw blank is passed through the hole in the washer and the threads are thereafter formed on the blank. The last thread portion, which is the thread portion closest to the head, holds the washer between it and the bottom of the head. In this way, the assembly can be more easily and efficiently used in various applications to create an assembly.
The design according to the present invention ensures that the washer will be centered around the shaft of the screw to provide an even load against the grounding terminal. Although the preferred embodiment shows the washer having a circular opening, the opening may have an oval shape or other suitable shapes according to the principles of the present invention. A feature of the invention is to provide a substantially even load distribution over the teeth of the grounding terminal to enhance the grounding effect. Another feature is that although the washer is flattened upon final assembly, it is adapted to be reusable. Yet another feature of the invention is that the grounding surface is substantially sealed from corrosion when the bearing surface on the ID is torqued down, and the outer bearing surface is flat against the grounding surface.
Although the invention will be further described in connection with the assembly shown in the attached drawings, the invention is capable of use in other applications, and the various assemblies illustrated are merely shown and described as examples of such applications.
Other features and advantages of the present invention will be readily apparent to those skilled in the art by a consideration of the detailed description of a preferred embodiment of the present invention contained herein.